The present invention relates to a method for counterfeit-proof of documents bearing a picture, preferably a passport picture.
The authenticity of documents used as printed work, for instance any sort of identity card verifying the own identity and/or proof of certain personal skills or authorization, is of particular official, economical and public interest especially as circulation of falsifications can lead to undreamed of loss of security as well as material loss.
When attaching or printing passport pictures onto official documents for authentication, it must be ensured that falsification is rendered impossible. Particularly, with the globalization of authorization sectors, greater attention must be paid to the authenticity of documents.
The current guarantees for protection against falsification by certification by the document issuer as well as by marking the to-be-protected document are still inadequate.
Although major efforts are being made to increase protection against falsification, with today""s technology, for example copying technology, it is easier to duplicate printed documents and circulate them as deceptively similar copies or forgeries.
Annually, falsification of documents bearing attached or printed on passport pictures cause great losses, e.g. to the German economy.
The main problem is due to that although the process of attaching or printing on a passport picture is falsification-proof, the authenticity of the passport picture itself can no longer be a unequivocally checked. Thus, the presumed to be safe process can be undermined by substituting a false passport picture. The use of digitized passport pictures increases the problem considerably.
The British publication GB 2 172 850 describes a process for increasing the protection against falsification of signatures by using two basic linear patterns of which at least one is provided with a superimposed grainy or scrambled pattern, which usually bears the signature data. When regarding only the pattern containing the signature, it is impossible to recognize the signature. With the aid of this process, the signature cannot be easily deciphered. The signature data is not optically filtered out of the grainy basic pattern and made visible until both patterns are superimposed. With the aid of this process, the signature cannot be easily deciphered. To do so requires the corresponding counter pattern. However, frequently, it is desired that the signature, whose duplication should be made difficult if not impossible, is quickly visible for control. Use of this known process would render, for instance, a passport picture completely unrecognizable, which is impractical for daily use.
The present invention provides a method for counterfeit-proofing documents bearing a picture, preferably a passport picture, by means of which the authenticity of a printed picture can be verified. The method marks the picture in such a manner that the marking does not impair the overall visual impression of the picture and also is largely resistant to environmental influences (scratches, stains, etc.) on the printed out picture.
The present invention relates to a method for counterfeit-proofing documents bearing a picture, preferably a passport picture, and provides the following steps:
Transferring the picture into a digital image file or having the picture as a digital image file, into which a secret image in binary form is incorporated in such a manner that the digital image file of the picture is divided into parquet cells whose number equals the number of image points of the secret image.
Forming a parameter function which allocates a bivalent output value to each parquet cell on the basis of parameter values, which describe each the image point, in such a manner the bivalent output value of all the parquet cells yields a bivalent position matrix.
Modifying the parameter values of the image points of the individual parquet cells with the aid of an optimizing process in such a manner that, first, the changes made to the image file of the picture of the document result in no visually perceivable changes and, secondly, the result of applying the parameter function to the individual parquet cells yields a bivalent position matrix which corresponds to the binary values of the secret image.
Attaching the picture containing the data of the secret image to the document or printing the picture containing the data of the secret image out together with document.
The present invention described here is a method that protects the passport picture itself against falsification and manipulation. This protection continues even after the passport picture has been attached or printed onto the document. The key factor is the falsification-proofness of printed works such as pictures or other graphic patterns.
Two units, a protection providing unit and an inspection unit, are required to carry out the invented method. The protection providing unit is based on a digitized form of the to-be-protected printed work, respectively a passport picture, and provides in the passport picture a binary image of low resolution in a scrambled state, i.e. encoded state, as a secret image in such a manner that the quality of the passport picture itself is minimally influenced, i.e. not perceivable with the naked eye. The printed out passport picture containing the secret image is attached to the document or is printed out together with the document. The inspecting unit, e.g. in the form of a manual device, is subsequently used at any desired time to make the secret image on the genuine document visible again. If the secret image can be restored from the passport picture, the document is an original. If the document is a forgery, the secret image cannot be made visible.
In this manner, the authenticity of the document can be verified not only by the document itself but also by the attached or printed on passport picture.
In order to increase the degree of protection, the secret image integrated in the to-be-protected passport picture can be provided with an additional password so that it is impossible to readout the secret image from the passport picture without giving the password. The public part of the password can be provided in a suited manner on the to-be-protected document respectively in the form of a bar code. The owner of the document with the passport picture has to know the private part for authentication.